The malaria parasite Plasmodium is transmitted by Anopheles mosquitoes, which inject infective forms called sporozoites into the host skin. Motile sporozoites rapidly travel to the liver and invade hepatocytes by forming a parasitophorous vacuole, where they transform into liver stages. After a few days of intense multiplication, liver stages release merozoites that invade erythrocytes, and are responsible for symtoms and complications of malaria. Sporozoite molecules interacting with hepatocytes during invasion represent ideal vaccine targets, simply because blocking liver infection prevents formation of merozoites and thus the pathogenicity associated with erythrocytic multiplication of the parasite. In this context, a better understanding of the molecular mecanisms of sporozoite invasion is essential. The nature of parasite and host molecules that interact during sporozoite invasion remains elusive. In this project, I propose to develop a targeted proteomic approach to specifically identify molecules that could play a role in the invasion process. To assess the functional importance of these candidate factors, I will perform targeted gene deletions. Using this strategy, I expect to identify novel sporozoite proteins that participate in parasite entry into hepatocytes. In parallel, I will develop an approach to visualize interaction of invading sporozoites with their target host cells, using transgenic parasites expressing fluorescent markers. This will be particularly helpful to decipher the role of parasite and host cell molecules during the process of invasion. Altogether, these approaches may lead to a better understanding of the process of sporozoite invasion, and to the discovery of potential new targets for novel intervention strategies aimed at blocking the first steps of malaria infection, before parasite development in the liver.

Neuronal circuits in the brain adjust their properties through regulation of both synaptic transmission and intrinsic neuronal excitability. Dysfunction of these regulations may lead to abnormal electrical activity and neurological deficits. Our proposal concerns the physiological and pathophysiological mechanisms that regulate global electrical activity and neurotransmission by modulating the Kv1 family of voltage-gated potassium channels. Kv1 channels are located at several strategic points of the neuron: the axon initial segment, the presynaptic terminal and along the conducting axon. They therefore determine several key properties of the neuron such as intrinsic excitability, synaptic strength, axonal conduction and synaptic timing, and have recently been implicated in the homeostatic plasticity of intrinsic neuronal excitability. Kv1 channels are regulated by leucine-rich, glioma-inactivated 1 protein (LGI1), a protein responsible for neurological diseases like autosomal dominant lateral temporal epilepsy (ADTLE) and limbic encephalitis (LE). We propose here to define i) the role of LGI1-dependent regulation of Kv1 in intrinsic plasticity, axonal function & synaptic transmission, ii) determine whether antibodies against LGI1 from patients with LE modulate excitability at the axon and the presynaptic terminal, and iii) identify the cellular mechanisms of epileptic seizures in LGI1-/-. This project combines complementary expertise of consortium members (D. Debanne, M. Seagar & S. Baulac) in cellular and molecular physiology of the synapse, and in neurogenetics of epilepsies. Our project will lead to identification of new mechanisms of activity-dependent plasticity in brain circuits that may help defining new strategies for therapeutic interventions.